I don't often see salt in that form around here as a pre-treatment. Most in this area use a liquid salt. When I worked for the municipal road crew in the 90's, we had magnesium chloride, not sure if that is still used or not. We had our spreaders outfitted with a sprayer system. If we were putting down the salt/anti-skid material after a snowfall, the system would be used to spray the material as it came out of the hopper and onto the spinner. Typically, the liquid would only be used at intersections. You could tell where it had been used. Now I see the tell-tale traces on the roadways when they have been sprayed as a pre-treatment - the whitish residue (the salt itself) after the liquid carrier dries. We didn't do that when I was doing that work - our snow preparation amounted to topping off the fuel in the plow trucks, putting the chains on the plow trucks, and loading the spreaders with the salt/anti-skid mix. Beginning of the season, the dump trucks that were the plow trucks would have stone put in the dump bed to act as ballast. We did not put the plows on the trucks in advance, or we would not be able to put them in the garage. The exception was the small dump truck and the 4WD pickup truck that were used to plow alley ways, cul-de-sacs, and clean up intersections after the big trucks came through.